1. Field of the Invention
The present invention relates to strapping machines for positioning and securing a binding strap around an object or objects, and more specifically, the present invention relates to an apparatus and method for maintaining tension on a strap end by mean of the inertia of rotating members of the apparatus.
2. Description of Related Art
Strap being pulled off of a strap coil of a strapping machine must be maintained at a particular tension for proper functioning of the strapping machine. In the past, several different types of apparatus and methods have been proposed for maintaining tension on the strap.
One prior art device requires a dancer arm with a spring clutch to apply a force to a strap segment, and belt brakes to stop coil rotation after cessation of strap pulling from the strap coil, in order to prevent slack and insufficient strap tension.
Another prior art device requires electrical or electromagnetic brakes to stop coil rotation.
Other prior art devices require electrical brakes to stop coil rotation and also require constantly rotating pull off wheels which constantly slip on the strap.
All of these prior art systems typically work only in the forward direction of strap pull, where strap is fed off of the strap coil.
The prior art tensioning devices do not function in the reverse, or rewinding direction.
All of the prior art systems are hampered by a general mechanical complexity. Dancer arms which function properly for various strap speeds and varying strap acceleration and deceleration conditions are difficult to design, and difficult to keep in adjustment. Also, the braking systems are generally complex, particularly the sensing and signalling systems for application and removal of the braking action against the coil.
The present invention solves the problem of maintenance of proper strap tension by providing an inertial system, eliminating the need for complex dancer arm and braking systems.
Because the strap is held in a substantially constant tension condition, the formation of strap loops which would otherwise fall off of the strap coil is prevented. Strap cross-over on the strap coil is avoided. Additionally, slack is removed from the strap gently, eliminating abrupt forces which would otherwise be applied to the strap and machine components during conventional strap tensioning.
The invention also solves the problems associated with stoppage of rotation of the rotating elements of the strapping machine, and rewinding strap out of the machine and back onto the coil.